A constitutive model for granular materials with grain crushing and its application to a pyroclastic soil     

Manuela Cecconi  Antonio DeSimone  Claudio Tamagnini  Giulia M.B. Viggiani 《国际地质力学数值与分析法杂志》2002,26(15):1531-1560

A constitutive model for granular materials is developed within the framework of strain–hardening elastoplasticity, aiming at describing some of the macroscopic effects of the degradation processes associated with grain crushing. The central assumption of the paper is that, upon loading, the frictional properties of the material are modified as a consequence of the changes in grain size distribution. The effects of these irreversible microscopic processes are described macroscopically as accumulated plastic strain. Plastic strain drives the evolution of internal variables which model phenomenologically the changes of mechanical properties induced by grain crushing by controlling the geometry of the yield locus and the direction of plastic flow. An application of the model to Pozzolana Nera is presented. The stress–dilatancy relationship observed for this material is used as a guidance for the formulation of hardening laws. One of the salient features of the proposed model is its capability of reproducing the stress–dilatancy behaviour observed in Pozzolana Nera, for which the minimum value of dilatancy always follows the maximum stress ratio experienced by the material. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The halo distribution of 2dF galaxies     

Manuela Magliocchetti  Cristiano Porciani 《Monthly notices of the Royal Astronomical Society》2003,346(1):186-198

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The Connection between Spheroidal Galaxies and QSOs     

G.L. Granato  G. DeZotti  L. Silva  L. Danese  M. Magliocchetti 《Astrophysics and Space Science》2002,281(1-2):497-500

In view of the extensive evidence of tight inter-relationships between spheroidal galaxies (and galactic bulges) with massive black holes hosted at their centers, a consistent model must deal jointly with the evolution of the two components. We describe one such model, which successfully accounts for the local luminosity function of spheroidal galaxies, for their photometric and chemical properties, for deep galaxy counts in different wavebands, including those in the (sub)-mm region which proved to be critical for current semi-analytic models stemming from the standard hierarchical clustering picture, for clustering properties of SCUBA galaxies, of EROs, and of LBGs, as well as for the local mass function of massive black holes and for quasar evolution. Predictions that can be tested by surveys carried out by SIRTF are presented. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

The solar soft X-ray background flux and its relation to flare occurrence     

Veronig  Astrid M.  Temmer  Manuela  Hanslmeier  Arnold 《Solar physics》2004,219(1):125-133

Solar Physics - The soft X-ray background flux (XBF) based on GOES 1–8&;nbsp;Å measurements for the period 1975–2003 is studied. There is strong evidence that in the XBF the...  相似文献   

Structural features and mechanical behaviour of a pyroclastic weak rock     

Manuela Cecconi  Giulia MB Viggiani 《国际地质力学数值与分析法杂志》2001,25(15):1525-1557

The results of an extensive programme of laboratory testing on intact and reconstituted samples of a pyroclastic weak rock from the volcanic complex of the Colli Albani (Central Italy) are presented. The deposit is known as Pozzolana Nera and may be assimilated to a bonded coarse grained material. The nature of bonds and the micro‐structural features were examined by means of diffractometry, optical and electron microscopy. As bonds are made of the same constituents of grains and aggregates of grains, bond deterioration and particles breakage upon loading are indistinguishable features of the mechanical behaviour. The testing programme consisted mainly of one‐dimensional and drained and undrained triaxial compression tests in a wide range of confining pressures up to 58 MPa. As confining stress increases, the mechanical behaviour of the material changes from brittle and dilatant to ductile and contractant; for both brittle and ductile behaviour failure is associated with the formation of shear surfaces separating the sample in several parts at the end of test. The experimental stress–dilatancy relationships are compared with the classical stress–dilatancy theories for a purely frictional material and for a material with friction and cohesion between particles. The analysis of the data indicates that peak strength results from the interplay between degradation of inter‐particle bonds, increasing friction between particles and increasing rate of dilation. Copyright © 2001 John Wiley & Son, Ltd.  相似文献   

The 2dF Galaxy Redshift Survey: the population of nearby radio galaxies at the 1-mJy level     

Manuela Magliocchetti  Steve J. Maddox  Carole A. Jackson  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto de Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Ofer Lahav  Ian Lewis  Stuart Lumsden  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,333(1):100-120

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Optical identifications of ∼4000 radio sources at the 1 mJy level     

M.Magliocchetti  S.J.Maddox 《Monthly notices of the Royal Astronomical Society》2002,330(2):241-250

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Dolomitic slates from Uruguay: petrophysical and petromechanical characterization and deposit evaluation     

Manuela Morales Demarco  Pedro Oyhantçabal  Karl-Jochen Stein  Siegfried Siegesmund 《Environmental Earth Sciences》2013,69(4):1361-1395

Slates are internationally known as roof and façade-cladding material since prehistoric times. The methods required to mine and manufacture these dimensional stones are relatively simple in comparison to those utilized in granitic dimensional stones. This has led to a worldwide rentable commercialization of slate in the last centuries and also to the development of characteristic cultural landscapes. In Uruguay several slates are mined and used in architecture, especially as façade cladding and floor slabs. The most important slates regarding their production and utilization are the dolomitic slates. These dolomitic slates are associated with the Neoproterozoic thrust and fold belt of the Dom Feliciano belt. Representative samples have been geochemically and petrographically characterized, as well as petrophysically and petromechanically analyzed. The petrophysical and petromechanical properties were investigated in a very systematic way with respect to the new European standards, showing values comparable to those registered for internationally known slates. Detailed structural and deposit analysis were carried out in Uruguay in order to evaluate the dolomitic slate deposits. The slates are linked to calc-silicate strata in a greenschist facies volcano-sedimentary sequence and the deposits are located in the limb of a regional fold, where bedding and cleavage are parallel. The main lithotype is a layered and fine-grained dolomitic slate with a quite diverse palette of colors: light and dark green, gray, dark gray, reddish and black. The mined slate is split into slabs 0.5–2 cm thick. In the past, the average production in Uruguay was around 4,000 tons/year and a historical maximum of 13,000 tons was reached in 1993 (Oyhantçabal et al. in Z dt Ges Geowiss 158(3):417–428, 2007). The oscillations in the regional demand were the cause of several flourishing and decay cycles in the activity, but our investigation shows a considerable volume of indicated resources and therefore a very good potential.  相似文献   

Thermospheric/mesospheric temperatures on Venus: Results from ground-based high-resolution spectroscopy of CO2 in 1990/1991 and comparison to results from 2009 and between other techniques     

Guido Sonnabend  Peter Krötz  Frank Schmülling  Theodor Kostiuk  Jeff Goldstein  Manuela Sornig  Dušan Stupar  Timothy Livengood  Tilak Hewagama  Kelly Fast  Arnaud Mahieux 《Icarus》2012,217(2):856-862

We report temperatures in Venus’ upper mesosphere/lower thermosphere, deduced from reanalyzing very high resolution infrared spectroscopy of CO₂ emission lines acquired in 1990 and 1991. Kinetic temperatures at ～110 km altitude (0.15 Pa) are derived from the Doppler width of fully-resolved single line profiles measured near 10.4 μm wavelength using the NASA GSFC Infrared Heterodyne Spectrometer (IRHS) at the NASA IRTF on Mauna Kea, HI, close to Venus inferior conjunction and two Venus solstices. Measured temperatures range from ～200 to 240 K with uncertainty typically less than 10 K. Temperatures retrieved from similar measurement in 2009 using the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) at the NOAO McMath Telescope at Kitt Peak, AZ are 10–20 K lower. Temperatures retrieved more recently from the SOIR instrument on Venus EXpress are consistent with these results when the geometry of observation is accounted for. It is difficult to compare ground-based sub-mm retrievals extrapolated to 110 km due to their much larger field of view, which includes the night side regions not accessible to infrared heterodyne observations. Temperature variability appears to be high on day-to-day as well as longer timescales. Observed short term and long term variability may be attributed to atmospheric dynamics, diurnal variability and changes over solar activity and seasons. The Venus International Reference Atmosphere (VIRA) model predicts cooler temperatures at the sampled altitudes in the lower thermosphere/upper mesosphere and is not consistent with these measurements.  相似文献   

Estimation of streamflow recession parameters: New insights from an analytic streamflow distribution model     

Ana Clara Santos  Maria Manuela Portela  Andrea Rinaldo  Bettina Schaefli 《水文研究》2019,33(11):1595-1609

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